Not a 'problem' here. I actually like the way you can flop the backrest down onto the drivers seat. My wife drops it down and forward to get it out of the way when she gets onto the passenger seat.MickeyF
Bob at Utopia has the quick release bracket which has to be mounted inside the seat just like the original bar. They are not cheap, but it solves the problem of the backrest "flopping down" if you only used a hitch pin.